1. Field of the Invention
This invention relates in general to submersible pump motors, and in particular to a bearing assembly which resists rotation. The bearing assembly supports the shaft in the motor.
2. Description of the Prior Art
A submersible pump is a centrifugal pump having a submersible motor that rotates the shaft to drive the pump. The motors for high volume oil and water production may be from six to sixty feet in length and be rated at several hundred horsepower. Each motor has a stator secured within a tubular housing. The stator is made up of thin disks, called laminations, that are magnetic and insulated from each other by coatings. Windings extend through the laminations to the stator.
A rotor secured to a shaft rotates within the stator. Because of the long length, the rotor is made up of a number of rotor sections. Each rotor section comprises a large number of flat metal disks, called laminations, that are secured by copper rods. The disks are insulated from each other by coatings. The rotor sections are spaced apart from each other, and a bearing assembly is located between each rotor section to maintain the shaft in axial alignment. The rotor sections are keyed to the shaft for rotation with the shaft, but are axially movable with respect to the shaft.
Each bearing assembly includes a sleeve keyed to the shaft for rotation. A bearing body fits slidingly on the sleeve. An elastomeric ring encircles the bearing body, acting as a bearing member. The motor is filled with oil, causing the elastomeric ring to expand and frictionally engage the inner wall of the stator. This engagement prevents the bearing body from rotating and supports the shaft in alignment.
As the motor heats up to operating temperature, the bearing body will expand slightly outward. Also, the shaft will likely grow longitudinally, causing the bearing body to move longitudinally with respect to the stator. Therefore, the bearing body must be precisely dimensioned so that it does not engage the stator wall so tightly as to create excessive thrust loads on thrust washers located above and below the bearing assembly. Also, the elastomer material used to construct the bearing member must be carefully designed so that the swelling due to oil in the motor is the correct amount.